Tailgate Light adjustable?

[Klis]

While tooling around with the tailgate I saw this and wondered what it could be. Anyone know what this is and what it does? It's part of the tailgate light. Looks like you'd turn it to adjust something...but what could it possibly ajust?

 

[L3it3R]

Looks like an anchor. Most light assemblies have them.

 

[Klis]

Probably

I wanted to twist/turn it but was too chicken

 

[ShockAuto]

the S taillights have that too, I removed it and it's just a molding plug I think